Ink transfer medium

ABSTRACT

An ink transfer medium, in particular a printing blanket, in particular a printing blanket for flexographic printing, has a cover layer for transferring an ink via a printing side and an adhesive layer for fastening the ink transfer medium to a base, in particular to a cylinder of a printing machine. The ink transfer medium is characterized by a support layer which is disposed between the cover layer and the adhesive layer, wherein the adhesive layer is disposed directly on that side of the support layer that faces away from the printing side, and wherein the support layer is a film/foil.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of international patentapplication PCT/EP2016/054184, filed Feb. 29, 2016 designating theUnited States and claiming priority from German application 10 2015 213057.6, filed Jul. 13, 2015, and the entire content of both applicationsis incorporated herein by reference.

FIELD OF THE INVENTION

The invention relates to an ink transfer medium, in particular aprinting blanket, in particular a printing blanket for flexographicprinting.

BACKGROUND OF THE INVENTION

In the field of flexographic printing, flexible printing plates whichcan be produced as printing blankets and can be wound onto the printingcylinder are used. A printing blanket usually has a multi-layeredconstruction. That layer that in the height is the external layer is thecover layer, the surface of the latter being aligned toward the objectto be printed and serving for transferring the ink. The relief to beprinted can be machined into the cover layer by means of laserengraving, for example, such that raised regions of the cover layer towhich the ink can adhere and be transferred to the surface of the objectto be printed can be configured (relief printing method). The depressedregions, the material of the latter having being removed by the laserengraving, for example, are not intended for the transfer of ink.

The printing blanket on that side of the cover layer that faces awayfrom the external surface of the cover layer can have a first wovenfabric layer as a first strength support layer which can serve forregulating the conveying behavior in the printing machine and serve forthe shape-related stability in the height (thickness) and in the widthof the printing blanket. Next, a compressible layer which can regulatethe hardness of the material of the printing blanket and the conveyingbehavior of the material can be provided.

A second woven fabric layer as a second strength support layer which canbe configured as a single-layer or multiple-layer woven fabric can bepresent as the fourth layer. This second strength support layer canlikewise serve for the dimensional stability in the height and in thewidth and additionally in the longitudinal direction, that is, in therevolving direction of the printing cylinder. The woven fabric can beconfigured so as to be natural, that is, from natural fibers, synthetic,that is, from chemical or man-made fibers, respectively, or so as to bea hybrid.

The fastening of the printing blanket to the smooth external side of theusually metallic printing cylinder can be performed by adhesive bonding.To this end, an adhesive layer which upon contact can produce amaterially integral connection to the external side of the printingcylinder, that is, to the external surface of the printing cylinder, canbe provided on the lower side of the printing blanket such as, forexample, on the internal surface of the second strength support layer,that is, on the internal side of the printing blanket that faces theprinting cylinder. This adhesive layer can usually be produced by way ofa double-sided adhesive tape.

It is disadvantageous in the use of a woven fabric as the secondstrength support layer that the woven fabric under the stress of use canlose thickness, that is, can collapse. The reason for this can beexplained in that the woven fabric fibers are composed of filamentswhich can contain air pockets. In the course of the use of the printingblanket, this air can be squeezed out of the woven fabric on account ofwhich this second strength support layer can be compressed in terms ofheight and thus become flatter. Therefore, the second strength supportlayer in this form can have an insufficient dimensional stability interms of height, that is, in terms of thickness.

It is furthermore disadvantageous that the second strength support layerby virtue of the woven fabric structure thereof toward the adhesivelayer can have a non-planar surface, that is, that the filaments of thewoven fabric can form an undulated surface. On account thereof, merelypunctiform contacts between the elevations of the woven fabric of thesecond strength support layer and the adhesive layer can arise, whichcan weaken the adhesive force between the adhesive layer and theremainder of the printing blanket. Furthermore, liquids such as, forexample, chemical printing inks which are used in printing can maketheir way into the porous woven fabric of the second strength supportlayer and cause the latter to swell, that is, enlarge the thickness ofthe second strength support layer. This can occur in particular on theperipheries such that a non-uniform thickness of the printing blanketcan arise, potentially compromising the quality of the printing. Also,the liquid that has been absorbed into the woven fabric can weaken theconnection between the adhesive layer and the second strength support.

SUMMARY OF THE INVENTION

It is an object of the invention to provide an ink transfer medium, inparticular a printing blanket, in particular a printing blanket forflexographic printing, such that the adhesive connection between theprinting cylinder and the printing blanket can be improved.

The object can, for example, be achieved by an ink transfer mediumhaving: a cover layer having a printing side and being configured totransfer an ink via the printing side; an adhesive layer for fasteningthe ink transfer medium to a base; a support layer disposed between thecover layer and the adhesive layer and having a first side facing awayfrom the printing side; the adhesive layer being disposed directly onthe first side of the support layer; and, the support layer being atleast one of a film and a foil.

The present invention thus relates to an ink transfer medium which ispreferably a printing blanket and particularly preferably is a printingblanket for flexographic printing. The ink transfer medium has a coverlayer for transferring an ink via a printing side. The cover layerrepresents the external layer in the outward direction, which canreceive ink and transfer ink to an object to be printed. The term“printing blanket” can thus mean a cylindrical printing plate as well asa planar printing plate, depending on the type of application and thetype of the printing method.

The ink transfer medium furthermore has an adhesive layer for fasteningthe ink transfer medium to a base, in particular to a cylinder of aprinting machine. On account thereof, the ink transfer medium can beconnected to the printing cylinder in a materially integral manner andin this way when in operation, that is, when printing, can be held onthe printing cylinder such that the cover layer, or the printing side ofthe latter, respectively, can assume its function.

The ink transfer medium is characterized by a support layer which isdisposed between the cover layer and the adhesive layer. Yet furtherlayers can be disposed between the cover layer and the adhesive layer.The adhesive layer here is however disposed directly on that side of thesupport layer that faces away from the printing side, such that optionalfurther layers can be disposed only between the cover layer and thesupport layer.

The support layer is furthermore a film/foil. This is to be understoodas a layer that in terms of height is very thin and which is composed ofa plastic material or of a metallic material, or comprises a plasticmaterial or a metallic material, respectively. A plurality of plasticmaterials or metallic materials, respectively, can be used in order forthe properties thereof to be utilized in a combined manner. Thefilm/foil is preferably composed of a plastic material. This cansimplify the production.

This invention herein is based on the concept that the support layer canbe produced from plastic or metal without any air pockets at all, or beproduced without air pockets which can degenerate in the course of theoperation of the printing blanket, respectively. The resilience in theheight of that layer of the printing blanket to which the adhesive layeradheres can be avoided in this way. This can lead to an increaseddimensional stability in the height. The longer service life of theprinting blanket that is caused on account thereof can lead to higherlife cycles and thus to lower costs.

It is also advantageous herein that cavities in this layer into whichliquids such as, in particular, printing chemicals can ingress, whichcould then cause the printing blanket to swell, can be avoided. Theseliquids could also have a negative effect on the adhesive connection andcompromise the effectiveness of the latter. The avoidance of theseproblems can increase the printing quality that is achievable by theprinting blanket as the printing plate, or can help sustain the printingquality.

It is furthermore advantageous herein that a film/foil from plastic ormetal as a support layer can have a very high shape-related stability interms of area, that is, in the width and in the longitudinal directionor the circumferential direction, respectively, of the cylindricalprinting blanket (in the printing direction). This is particularlyadvantageous with a view to engraving the cover layer, because themotive that is engraved in the cover layer and is to be transferredshould have as high a positioning accuracy (register stability) aspossible, and the latter can be facilitated by a high shape-relatedstability of the printing blanket in terms of area. Shape-relatedstability of the printing blanket herein is to be understood as that thematerial of the printing blanket at the operative point, or in theoperating region, respectively, has a high rigidity, that is, has a highincrease in force accompanied by low elongation. This herein is anelastic deformation (a straight line according to Hooke's law), that is,a linear correlation between force and elongation.

A double-sided adhesive tape which can be applied to the lower side ofthe support layer can be used as the adhesive layer. Alternatively, thelower side of the support layer can also be provided with a layer ofapplied adhesive means.

According to an aspect of the present invention the film/foil inrelation to the adhesive layer has a smooth surface. A smooth surface isunderstood to be a roughness Rz of equal to or less than 10 μm. Thisaspect of the invention herein is based on the concept that an adhesiveeffect can be all the more positive the larger the planar contactbetween the surfaces to be connected. The adhesion in relation to theadhesive layer, both as a double-sided adhesive tape or else as acoating of adhesive means, can be improved by way of as smooth a surfaceof the support layer as possible. This can increase the life cycle ofthe printing blanket and thus cause a cost saving.

According to a further aspect of the present invention, the film/foil isa plastic film which is composed of polyester, or comprises polyester,respectively. As a plastic, this material can meet the aforementionedproperties, and thus attain the advantages that are achievable onaccount thereof. Moreover, polyester is cost-effective in the productionand is easy to process. Furthermore, a support layer from polyester canalso cause a high dimensional stability in terms of area, that is, inthe width and in the longitudinal direction.

According to a further aspect of the invention, the film/foil is a metalfoil which is composed of metal, or comprises metal, respectively. Theaforementioned properties and advantages can be implemented in thealternative manner by way of a thin metal foil as the support layer.

According to a further aspect of the present invention, the adhesivelayer is disposed as a double-sided adhesive tape by way of winding. Onaccount thereof, the adhesive layer can be applied to the printingblanket in a simple and rapid manner on site, that is, directly onto theprinting cylinder, such that the adhesive layer does not have to beapplied in advance and be protected from drying out and/or fromcontamination, which could represent an additional effort. Also, thedecision as to which locations, or to which thickness, respectively, theadhesive tape is to be applied or disposed, respectively, between theprinting blanket and the printing cylinder can be made directly on theprinting cylinder.

According to a further aspect of the present invention, the adhesivelayer is disposed on the film/foil by way of application. Theapplication can be performed by spraying or wetting, for example. Thiscan preferably be performed as the last method step in the context ofthe production of the printing blanket. The applied adhesive layer canthereafter preferably be provided with a protection against drying outand/or contamination.

It is advantageous herein that the printing blanket together with theadhesive layer can be shipped to the printing press or the like, suchthat the printing blanket there can be directly, or optionally upon theremoval of a protective layer, applied to the printing cylinder by wayof the adhesive layer. This can simplify and accelerate the fitting tothe printing cylinder.

According to a further aspect of the present invention, the ink transfermedium furthermore has a strength support layer which is disposedbetween the cover layer and the support layer. The strength supportlayer is preferably disposed directly between the cover layer and thesupport layer. The strength support layer can serve for regulating theconveying behavior in the printing machine and serve for theshape-related stability in the height (thickness) and in the width ofthe printing blanket.

According to a further aspect of the present invention, the ink transfermedium furthermore has a compressible layer which is disposed betweenthe cover layer and the support layer, preferably between the strengthsupport layer and the support layer. The compressible layer preferablyhas a compressibility of more than 150 μm at an impingement of 135N/cm². The compressible layer is preferably disposed directly betweenthe cover layer and the support layer, or directly between the strengthsupport layer and the support layer, respectively. The hardness of thematerial of the printing blanket and the conveying behavior of thematerial can be regulated by way of the compressible layer.

According to a further aspect of the present invention, the cover layeris composed of an elastomeric material, or comprises an elastomericmaterial, respectively. It is advantageous herein that the cover layerin this way can have a good engraving capability.

According to a further aspect of the present invention, precisely thefollowing layers are present from the outside to the inside, and as theink transfer medium are disposed in this sequence:

cover layer,

strength support layer,

compressible layer,

support layer, and

adhesive layer.

The use of all these layers causes the advantages that have beendescribed individually above. The disposal of the layers in thissequence can ensure the optimal effect of the individual layers.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described with reference to the drawingswherein:

FIG. 1 shows a lateral schematic sectional illustration of an inktransfer medium according to the prior art; and,

FIG. 2 shows a lateral schematic sectional illustration of an inktransfer medium according to an embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

FIG. 1 shows a lateral schematic sectional illustration of an inktransfer medium 1 according to the prior art. The ink transfer medium 1is a printing blanket 1 which in the state in which the latter is spreadout in a planar manner, for example after production or when being cutto size, extends in a horizontal plane in a longitudinal direction Y anda transverse direction (not illustrated). The height Z, or the thicknessZ, respectively, extends perpendicularly thereto. If the printingblanket 1 is cut to size and attached to a printing cylinder (notillustrated), the longitudinal direction Y thus becomes thecircumferential direction Y in which the printing blanket 1 as theprinting plate 1 is disposed about the cylindrical circumference of theprinting cylinder.

The upper side of the printing blanket 1 in the illustration of FIG. 1herein represents the upper side of the printing blanket 1 which becomesthe external side of the printing plate 1. Accordingly, the lower sideof the printing blanket 1 in the illustration of FIG. 1 hereinrepresents the lower side of the printing blanket 1 which becomes theinternal side of the printing plate 1.

In the height Z the printing blanket 1 of FIG. 1 according to the priorart has a cover layer 10 which in the case of the printing plate 1 canbe referred to as the cover plate 10. The upper external side of thecover layer 10 represents the printing side 11 of the cover layer 10which, for example by laser engraving, can be used for configuring arelief. For this reason, the cover layer 10 preferably has apredetermined minimum thickness in order to offer sufficient material inthe height Z, which permits the configuration of sufficiently clearcontours of the motive. For example, the cover layer 10 in the height Zcan have a thickness of at least 0.3 mm.

On the opposite side of the cover layer 10 a first strength supportlayer 12 in the form of a woven fabric layer 12 is disposed, the latterserving for regulating the conveying behavior in the printing machineand serving for the shape-related stability in the height Z and in thewidth of the printing blanket 1. A compressible layer 13 which regulatesthe hardness of the material of the printing blanket 1 and the conveyingbehavior of the latter is disposed as the next layer.

Thereafter, a second strength support layer 14 which likewise serves forthe dimensional stability in the height Z and in the width as well asadditionally in the longitudinal direction Y is provided as a secondwoven fabric layer 14. An adhesive layer 16 in the form of adouble-sided adhesive tape 16 by way of which the printing blanket 1 canbe adhesively bonded onto the printing cylinder is disposed on the lowerside of the second strength support layer 14.

The second strength support layer 14 has a two-ply woven fabric, thefilaments or threads, respectively, thereof lying on top of one anotherin an alternating manner. On account thereof, punctiform elevationswhich are surrounded by depressions, or regions that in the height Z areflatter, respectively, are formed in the height Z both in relation tothe compressible layer 13 as well as in relation to the adhesive layer16. In this way, there are only punctiform materially integral contactsat least between the adhesive layer 16 as the double-sided adhesive tape16 and the second strength support layer 14, on account of which theadhesive effect between these two layers 14, 16 is weakened. Cavitieswhich can receive air are also formed in the second strength supportlayer 14, the air escaping being able to weaken the dimensionalstability of the printing plate 1 in the height Z over the period ofoperation of the printing plate 10. Also, liquids such as, for example,printing chemicals, can ingress into these cavities and cause the secondstrength support layer 14 to swell.

FIG. 2 shows a lateral schematic sectional illustration of an inktransfer medium 1 according to an embodiment of the present invention.Instead of the second strength support layer 14 as the second wovenfabric layer 14, according to an aspect of the invention a support layer14 from polyester is disposed between the compressible layer 13 and theadhesive layer 16. Air pockets can be avoided in this way, such that ahigher dimensional stability of this layer 15 can be achieved in thelongitudinal direction Y, in the transverse direction, and in the heightZ. Cavities into which printing chemicals could ingress can also beavoided in this way. This leads to an improved printing quality and to ahigher service life of the printing blanket 1 according to theinvention.

It is understood that the foregoing description is that of the preferredembodiments of the invention and that various changes and modificationsmay be made thereto without departing from the spirit and scope of theinvention as defined in the appended claims.

LIST OF REFERENCE SIGNS Part of the Description

-   Y Longitudinal direction, circumferential direction-   Z Height, thickness-   1 Ink transfer medium, printing blanket, printing plate-   10 Cover layer, cover plate-   11 Printing side of the cover layer 10-   12 First strength support layer, first woven fabric layer-   13 Compressible layer-   14 Second strength support layer, second woven fabric layer-   15 Support layer, film/foil, plastic film, metal foil-   16 Adhesive layer, double-sided adhesive tape, adhesive coating

What is claimed is:
 1. An ink transfer medium comprising: a cover layerhaving a printing side and being configured to transfer an ink via saidprinting side; an adhesive layer configured to fasten the ink transfermedium to a base; a support layer disposed between said cover layer andsaid adhesive layer and having a first side facing away from saidprinting side; said adhesive layer being disposed directly on said firstside of said support layer; and, said support layer being at least oneof a film and a foil.
 2. The ink transfer medium of claim 1, whereinsaid at least one of a film and a foil has a smooth surface in relationto said adhesive layer.
 3. The ink transfer medium of claim 1, whereinsaid support layer is a plastic film comprising polyester.
 4. The inktransfer medium of claim 1, wherein said support layer is a metal foilcomprising metal.
 5. The ink transfer medium of claim 1, wherein saidadhesive layer is disposed as a double-sided adhesive tape by way ofwinding.
 6. The ink transfer medium of claim 1, wherein said adhesivelayer is disposed on said support layer by way of application.
 7. Theink transfer medium of claim 1 further comprising a strength supportlayer disposed between said cover layer and the support layer.
 8. Theink transfer medium of claim 1 further comprising a compressible layerdisposed between said cover layer and said support layer.
 9. The inktransfer medium of claim 7 further comprising a compressible layerdisposed between said strength support layer and said support layer. 10.The ink transfer medium of claim 1, wherein said cover layer comprisesan elastomeric material.
 11. The ink transfer medium of claim 1, whereinsaid cover layer consists of an elastomeric material.
 12. The inktransfer medium of claim 1 further comprising: a strength support layer;a compressible layer; and, wherein said cover layer, said support layer,said adhesive layer, said strength support layer, and, said compressiblelayer are disposed in the following sequence: cover layer, strengthsupport layer, compressible layer, support layer, and adhesive layer.13. The ink transfer medium of claim 1, wherein the ink transfer mediumis a printing blanket.
 14. The ink transfer medium of claim 1, whereinthe ink transfer medium is a printing blanket for flexographic printing.15. The ink transfer medium of claim 1, wherein said adhesive layer isconfigured to fasten the ink transfer medium to a cylinder of a printingmachine.
 16. The ink transfer medium of claim 1, wherein said supportlayer is a plastic film consisting of polyester.
 17. The ink transfermedium of claim 1, wherein said support layer is a metal foil consistingof metal.